1. Field of the Invention
The present invention relates generally to the field of marine seismic data acquisition, in particular to ocean bottom seismic (OBS) recording, and deployment and retrieval of seismic receivers.
2. Description of the Related Art
Oil and gas exploration and production professionals rely heavily on seismic data in their decision making. Seismic data is collected by introducing energy into the earths surface (known as shooting or a shot), recording the subsequent reflected, refracted and mode converted energy by a receiver, and processing these data to create images of the structures beneath the surface. Imaging the earth in this manner is complex and requires accurate information regarding the source and receiver locations that produced these data.
Both 2D and 3D seismic surveys are carefully preplanned. The planned locations for each shot and each seismic receiver is calculated so as to achieve the geophysical objectives of the survey, and the operations personnel attempt to follow the plan as accurately as possible. Some conventional methods used to record seismic data in marine environments create numerous challenges relating to accurate positioning of receivers, surface or subsurface noise, equipment malfunction and breakage, among other challenges.
For 4D seismic data collection and in other types of deep ocean seismic acquisition programs utilizing autonomous ocean bottom seismic receivers, the receivers are placed on and retrieved from the ocean bottom with expensive heavy work class remote operating vehicles (ROV's). While the use of ROV's provides highly accurate placement of the receiver units, the use of ROV's, and their associated vessels and support crews, is costly. It is not uncommon for ROV operations to exceed half the costs of the entire seismic survey. For example, the ROV operating costs may, in many cases, exceed 50 percent of the entire seismic program cost. Further, the heavy work class ROV's utilized in deep water applications are highly complex machines which are subject to mechanical failures. For this reason multiple ROV's are often employed. Still, ROV failures may delay the seismic operation for a prolonged period, further increasing the cost of the seismic survey.
Therefore, there exists a need for an apparatus and method for ensuring accurate positioning of seismic devices on the seafloor in deep water applications that is less expensive to maintain and operate.